Summary At around 1820, whilst discharging cars at Gabriola Island, British Columbia, the BowenQueen spontaneously backed off the dock, causing the shore-mounted vehicle ramp to fall below the level of the vessel's vehicle deck. There was a gap of about four metres between the ferry and the ramp, however the deck crew acted promptly to stop the discharge of vehicles. There was no injury. Ce rapport est galement disponible en franais. Factual Information Particulars of the Vessel Description of the Vessel The BowenQueen is a double ended ro-pax coastal ferry, designed to carry 70cars on one main deck and 387 foot passengers on two upper decks (seePhoto1). Propulsion and steering is by means of four right-angled drive (RAD) units, one at each corner of the hull. The RADs are of the azimuth turning type, free to rotate through 360and are independently powered by unidirectional diesel engines, via fluid couplings. They can be directly controlled from two locations in the wheelhouse or from the engine room. When in regular service, the RADs are controlled from the wheelhouse. Photo1. Aerial view of vessel showing wheelhouse, vehicle deck and double ended features. Each wheelhouse control console overlooks its half of the vehicle deck and by means of a 'transfer' switch, becomes the active or 'live' control station. There are two 'joystick' type control heads at each console and one pair of 'end' RADs is controlled by each joystick (seePhoto3). The vessel being double-ended, either console can be used for manoeuvring. Description of Steering Control Systems Steering the vessel is effected by rotating the RADs and pointing the propellers in the desired direction. The rotation of a RAD leg is done via gearing and by a hydraulic motor powered by an engine-driven hydraulic pump. The direction of rotation of a RAD unit is controlled by an electro-hydraulic 'proportional' valve, which in turn receives its signals from a control head in the wheelhouse. The vessel's propulsion and steering system may be operated in either the automatic or manual modes. The manual mode is essentially a back up system. Automatic Control System for Right Angle Drive Units The joystick type control head is used to manipulate the throttle and clutch and can rotate a pair of end RAD units through 360in the horizontal plane. Pushing the handle forward has the effect of speeding up the engines and propellers; pulling it vertically upwards disengages the clutches; while rotating the handle causes the drive legs to rotate. By means of suitable gearing, these motions are communicated to transducers which in turn communicate with automatic throttle, clutch and steering control units. A transfer control switch serves to engage or disengage the appropriate control station in the wheelhouse. The automatic steering control unit contains 'power supply', 'servo' and 'positive direction process control' printed circuit boards (PCBs or cards), which modulate and convert the input signals into an output signal, which is used to control the hydraulic proportional valves. These hydraulic valves are then used to turn the RAD legs in the required direction. A feedback transmitter is incorporated in the control process. It provides positional information back to the servo card, where the signals are compared and suitable error signals generated. In this way, the control process is of the 'closed loop' type. 'Manual' or Jog Steering Mode Figure1. Process control flow chart In this mode, the automatic steering control unit is bypassed and the hydraulic valve is directly controlled by the 'Jog' steering switch (seeFigure1). Each RAD leg has its own jog switch and the switch itself has three positions - the centre position being 'zero' or neutral, while the two positions at either side of the centre rotate the RAD either clockwise or counterclockwise. This rotation is sustained as long as the switch is held in position. The switch is spring loaded to return to its centre, 'neutral' position upon release. This effectively stops further rotation of the RAD. Alarm System The steering control system is equipped with audio-visual alarms in both the engine room and wheelhouse, which give warning in the event of failures of the power supply, prime movers, hydraulic pumps or motors. Description of a Typical Docking and Undocking Manoeuvre The crossing is normally performed at full-service speed, with all four RADs thrusting in the 'ahead' direction. Upon approaching the dock, the vessel is progressively slowed down and aligned, so that it creeps towards the 'vee' formed by the wing-walls of the dock. The two forward RADs are then rotated so that they thrust in the opposite or 'astern' direction. This provides a braking action to the vessel's movement and allows it to come to a gentle stop against the fenders of the dock. The two after RADs are throttled up slightly to maintain a net positive thrust against the dock and the two forward RADs are then re-rotated back into the 'ahead' direction. Once all the RADs are pointing in the same 'ahead' direction and the officer in charge of the wheelhouse (OOW) is satisfied that conditions have stabilised, the 'off loading officer' is signalled to prepare for discharge. The shore ramp is lowered onto the vehicle deck by remote control, securing lines are passed between the vessel and the shore and the protective netting across the deck is removed. Foot passengers leave the vessel first, followed by vehicles. The vessel then loads for the return trip. Upon confirmation that loading has been completed, the shore ramp raised and the securing lines released, the OOW transfers control of the RADs to the other wheelhouse control console for departure. The two joysticks are then rotated simultaneously so that all four RADs move together through 180; the propellers are now thrusting in the new 'ahead' direction and the vessel proceeds outwards. History of the Voyage The BC ferry corporation vessel Quinsamis the regular vessel used to provide ferry services between Gabriola Island and Nanaimo, British Columbia. On 04February2002 it went in for an extensive refit and was replaced by the BowenQueen. The regular working crew of the Quinsamhad been familiarised on the running of the BowenQueen and began operating it from February4onwards. Photo2. View of vehicle deck and a loading operation as the ferry is pushing against the wing walls of the dock. At about 1755 on 13April2002, the BowenQueen departed Nanaimo Harbour for the scheduled crossing to Descanso Bay, Gabriola Island. The crossing was uneventful and the vessel arrived at Descanso Bay at 1820. When in position at the dock the master aligned all four RADs in the 'pushing in' direction, the shore ramp was lowered and the discharging of foot passengers and vehicles commenced. After docking, the master was alone in the wheelhouse and working at the chart table, when the chief officer entered the wheelhouse to relieve him. He checked that the joysticks at both the 'live' and the 'nonactive' control consoles were in the same angular position and after verifying this, moved toward the chart table, as the master began to descend the wheelhouse stairs. At this time the chief officer noticed that the vessel was moving astern. He alerted the master who immediately ran toward the 'live' control console to find that the vessel, now some four metres off the dock, had begun moving toward it again, although no one had altered the control settings. The astern movement of the ferry caused it to part its mooring lines and the shore ramp to fall below the level of the car deck. Three motor vehicles had been discharged and a fourth was on the ramp when the vessel began moving away from the dock. The deckhand in charge of the car deck shouted for the driver of the fourth car to accelerate, allowing it to clear the ramp. Further off-loading was stopped. The deckhand's vigilance and timely action prevented any casualties. Meanwhile in the wheelhouse, the master had declutched all four RADs, rotated the two forward legs so that they would provide a braking action and then re-clutched them in. The vessel was backed away from the ramp and did not make contact with it. It was then taken about 30m away from the dock, where the four RAD units were operationally tested to determine the cause of the malfunction. When none was found, the ferry returned to its berth and safely discharged all the remaining cars. Photo3. View of control console showing control heads, jog steering and rudder angle indicators. Shore authorities were notified of the incident and, with the vessel in the dock, the ship's crew carried out further tests on the legs and their hydraulic and electronic control systems, in an attempt to determine the cause. No abnormality was found and the vessel resumed its normal operations. It was estimated that the BowenQueen had been discharging passengers and cars for about four minutes before it began moving astern and that the time taken for the vessel to back away from the berth and then move towards it again, was about 10to 15seconds. It was also reported that the vessel's spontaneous departure from the dock was more rapid than the normal 'controlled' undocking manoeuvre and that the vessel had initially moved sideways and pushed against the port wing wall. Vessel and Crew Certification The BowenQueen was certificated, equipped and crewed in accordance with existing regulations. Additionally, the BCFerry Corporation and the vessel held valid certification in accordance with International Safety Management Code requirements.